Arendt et al. (2002) concentrates on Alaskan glaciers but the points made are relevant to glaciers around the world and the findings they report are thought provoking with regard to sea level change and the contribution that melting mountain glaciers could have. Arendt et al. (2002) starts by highlighting some of the problems that have plagued glacial scientists in the past, showing how difficult measurement of retreat is due to the number of glaciers and the size of some of the larger glaciers.
Arendt et al (2002) criticise previous findings; in particular the fact that mountain glaciers have contributed to sea level rise, adding 0.2-0.4mm/year for the last century (Persson, 1996). Why? Simply the fact that there has been insufficient measurements of glacier mass balance to be able to draw up firm conclusions on the worlds glaciers. Obviously sampling every one of the worlds 160,000+ glaciers would be a costly and time consuming job; so there are only 40 glaciers worldwide that have been monitored for over 20 years. Of these 40 glaciers few are high latitude glaciers and most of them have been selected because of the ease of access and their small size, not because they are representative of the majority of glaciers (Arendt et al. 2002). In Alaska there are three glaciers that are monitored, all three are small glaciers, past studies have used the data from these glaciers as representative of all Alaska’s Glaciers with regards to the contribution they make to sea level rise.
Technology continues to develop and Arendt et al (2002) use this technology to more effectively find the extent to which Alaskan mountain glaciers have contributed to sea level rise. Using airborne laser altimetry to measure the volume of 20% of the glaciers in the Alaska region. They measure a total of67 glaciers to predict more accurately the contribution of Alaskan glaciers to global sea rise. This technique likely represents the future of how glacier retreat is measured and certainly the results from this are more reliable than the data collected using only 4 glaciers.
The results
The laser altimetry shows that glacial thinning in the area has become more prevalent in recent years (twice as fast in the last 5 years, compared to the thinning from the mid 1950’s to the mid 1990’s). The results are substantially different to previous estimations of contribution to sea level change. Arendt et al. (2002) found that Alaskan glaciers contributed 9% of the observed sea-level rise (1.5mm/year +/-0.5mm) over the last 50 years and in the last decade this figure could be as large as 3.2mm/year. Clearly previous estimates of the contribution must be questioned, not just for Alaskan glaciers but for estimations made around the world.
“Mountain glaciers may be contributing a substantial fraction of the increased rate of sea level rise suggested by satellite observations from 1993 to 1998” (Arendt et al., 2002; 385). A statement that clearly implies the major percentage of sea level rise that is likely attributable to glacial melt.
My View
This post can be split in to two separate parts in my opinion. The first being the past problems with observing glaciers. Clearly scientists in the past have not had sufficient data to be accurate in their predictions. Whilst Arendt et al (2002) show how progression can be made by using technology to assess glaciers they still only sample 20% of the glaciers in the region and so we still cannot be 100% sure of what is taking place with regard to the glacial mass balance. Unfortunately the sampling of 100% of the worlds glaciers is not likely to take place in the near future and so we must do what we can with the data available to prepare for the changes that may come about in the world.
The second part of the article shows the significant contribution made by Alaskan glaciers to sea level change. Just under 10% is highly significant proportion and it would be fascinating to know the percentage of contribution from glaciers worldwide. Needless to say it would likely be a large proportion and means that we should be looking at how best to control the rate of melting that is taking place.
“Mountain glaciers may be contributing a substantial fraction of the increased rate of sea level rise suggested by satellite observations from 1993 to 1998” (Arendt et al., 2002; 385). A statement that clearly implies the major percentage of sea level rise that is likely attributable to glacial melt.
My View
This post can be split in to two separate parts in my opinion. The first being the past problems with observing glaciers. Clearly scientists in the past have not had sufficient data to be accurate in their predictions. Whilst Arendt et al (2002) show how progression can be made by using technology to assess glaciers they still only sample 20% of the glaciers in the region and so we still cannot be 100% sure of what is taking place with regard to the glacial mass balance. Unfortunately the sampling of 100% of the worlds glaciers is not likely to take place in the near future and so we must do what we can with the data available to prepare for the changes that may come about in the world.
The second part of the article shows the significant contribution made by Alaskan glaciers to sea level change. Just under 10% is highly significant proportion and it would be fascinating to know the percentage of contribution from glaciers worldwide. Needless to say it would likely be a large proportion and means that we should be looking at how best to control the rate of melting that is taking place.
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